Gila monster
Conservation Messaging Opportunities
Physical features
Gila monsters are considered a large lizard and can reach lengths of one to two feet and weights of three to five pounds. They have short, fat tails and stout limbs with large claws.
Their skin has a bumpy texture and is black with contrasting scales in red, yellow, or orange.
They are solitary creatures that are inactive most of the day and hide in burrows or under rocks. They are active during the early morning to avoid heat in the summer, while some even hibernate in the summer and live off extra fat in their tail.
Like snakes, Gila monsters hunt with their senses of taste and smell. They have a forked tongue that they use to pick up the scent particles of perspective prey.
Range and Habitat
Range – South Western United States and into Mexico
Habitat – Arid areas with scattered brush and cacti
Diet: Carnivore
Wild – Small mammals, birds, lizards, and eggs
Zoo – Mice
Lifespan
Wild – Unknown
Zoo – 20+ years
An individual at Zoo Atlanta turned 37 years old in September 2023.
Reproduction
Mating usually occurs during May.
Females are oviparous and produce one to twelve eggs per year which are laid in an underground cavity. Incubation of the eggs generally lasts about ten months.
Hatchlings are brightly colored and about four inches in length.
Conservation: Near Threatened
Ranked Appendix II by CITES
Major threats: hunting, habitat destruction, illegal collection
They are often killed because they are venomous and falsely viewed as a danger.
Interpretive Information
In addition to being venomous, the Gila monster's bold, distinctive patterning is a form of aposematism.
Venom is rarely used on prey, which largely consists of eggs and nestling animals. This suggests that it is only used in defense.
Unlike snakes, a Gila monster’s venom is not injected into the blood stream. They have a vice-like bite that can make up to a half inch deep wound and the venom is entered into the blood stream through the bite. They can further envenom a predator by chewing or tearing at the skin.
They can eat large amounts of food at one time which is advantageous because available prey can be inconsistent at times. Young Gila monsters can eat up to 50% and adults can eat up to 35% of their body weight at a time.
Gila monster bladders act as canteens. They drink as much water as possible during the rainy months, and that water is maintained by the bladder which helps keep them hydrated during the dry season.
References
CITES. (2006). Gila Monster. Retrieved December 10, 2006, from CITES Species Database Web site: http://www.cites.org/eng/resources/species.html
Davis, Jon R., and Dale F. DeNardo. "The urinary bladder as a physiological reservoir that moderates dehydration in a large desert lizard, the Gila monster Heloderma suspectum." Journal of Experimental Biology 210.8 (2007): 1472-1480.
Hammerson, G.A., Frost, D.R. & Gadsden, H. 2007. Heloderma suspectum. The IUCN Red List of Threatened Species 2007: e.T9865A13022716. https://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T9865A13022716.en. Accessed on 27 October 2023.
Hamlett, L. (Unknown). Gila Monster. Retrieved December 10, 2006, from the Nashville Zoo at Grassmere Web site: http://www.nashvillezoo.org/gila.htm
Smithsonian National Zoological Park. (Unknown). Reptiles & Amphibians: Gila Monster. Retrieved December 10, 2006, from the Smithsonian National Zoological Park Web site: http://nationalzoo.si.edu/Animals/ReptilesAmphibians/Facts/FactSheets/Gilamonster.cfm
Stewart, M. (2003). Heloderma suspectum. Retrieved December 9, 2006, from the Animal Diversity Web Web site: http://animaldiversity.ummz.umich.edu/site/accounts/information/Heloderma_suspectum.html
Zoo Atlanta Animal Care Team
Updated January 2024